Animal Play brings together the major findings about play in a wide range
of species including humans. Topics include the evolutionary history of play,
play structure, function and development of play, and sex and individual differences.

Abstract: Reviews recent data suggesting that object, locomotory, and social play
do occur in some turtles. The author describes phenomena that, if seen in a mammal
or bird, would readily be labeled playful by most observers. These examples are
compared in detail with frequently noted criteria for play. The author believes
that these examples may aid in identifying the primary processes by which "play"
originated and evolved in ancient vertebrates and their modern descendants. Understanding
the origins of play may provide the framework from which the highly diverse and
complex structures of mammalian and avian play could evolve through a series of
secondary or derived processes. The author believes that play may be an important
aspect of behavioral innovation in the evolution of vertebrates and outlines some
of the lessons turtle might teach readers.

Abstract: Discusses the definition and purposes of play behavior in ravens. The
authors include observations of ravens held in an outdoor enclosure to provide
the reader with a sense of the nature of raven play. The chapter also covers object
exploration and manipulation, play catching, flight play, bathing, sliding and
hanging, as well as allospecific interactions and vocal play. The authors discuss
the relationship of these behaviors to aspects of raven biology and ecology.

Abstract: Discusses the definitions of object play, and includes a brief description
of object play by juveniles to serve as a comparison. The focus of this chapter
is object play by adult animals, a type of behavior that is less commonly observed
than juvenile play and perhaps even more resistant to explanation. The author
covers the structure and function of adult play behavior, as well as object play
behavior in adult predatory animals. Experimental evidence for the association
of predation and object play in adults is cited and directions for future study
of object play by adult are suggested.

Abstract: Summarises and compiles the existing data on play in the Macropodoidea
(kangaroos). The first part of the review discusses the quality of the available
data. Data quality affects the limits to which it can be confidently used to answer
functional and evolutionary questions. The generally poor quality of the data
for macropodoids explains why functional and evolutionary generalisations regarding
play are currently premature and sets a basis for understanding why there may
be confusion as to what is and what is not play in macropodoids. Following this
is a review of play in macropodoids: what types of play occur and their main structural
elements. The relationship between play and real fighting is examined in the third
part of the review. The observations that some of the ritualised fights described
in the literature often include characteristic features of play seen in placentals
are addressed. Rather than reflecting a taxonomic difference in the fighting behavior
between macropodoids and placentals, it is argued that some of these fights were
misclassified play fights. Finally, the function and evolution of play in macropodoids
are discussed.

Abstract: Examines intentional communication and social playing in animals.
The chapter covers the evolution, definition of play, including discussion of
the possibility of an evolutionary biology of play and the intentionality of
play. The authors discuss play signals, and also look at the broader cognitive
context of play. The chapter concludes with remarks on social play and comparative
studies of animal cognition. Full
text (Cogprints -- external).

Abstract: Discusses the case for play fighting in animals as having the function
of rehearsing adult combat. The authors state that the idea would be more compelling
if the structure of play fighting had design features suitable for this purpose.
The chapter shows that the very behavioral features that make play fighting play,
also make play fighting a poor means of rehearsing combat skills. While some evidence
suggests that such rehearsal may occur for some combat tactics in some situations,
the practice hypothesis cannot account for the form of play fighting in most species.

Miller, Michelle N. and John Alexander Byers. Sparring
as play in young pronghorn males. Bekoff & Byers (1998), p. 141-160.

Abstract: Attempts to determine what the purpose and wager is between sparring
ungulate males. To answer this question the authors describe the context in which
sparring is observed as well as the common participants in both pronghorn and
other species in which sparring has been studied. In this and other recent studies,
there has been an attempt to quantify, rather than simply describe, sparring in
a manner that will help to resolve its functions. The authors define sparring
and describe the form it takes in various organisms. They then present a detailed
analysis of sparring in young pronghorn males.

Abstract: Examines the case for a cognitive training function of play fighting
in squirrel monkeys. The author examines the role of dominance in play, and how
dominance relationships determine play decisions. Also considered is the importance
of winning vs. the play experience itself. Finally, the author covers the benefits
and costs of play fighting, including possible risks and concludes the chapter
with a consideration of play as training for serious fighting.

Abstract: Considers several aspect of animal play that seem inadequately explained
by current theory. These include (1) the possible implications of the brief, repetitive
nature of play behaviors, (2) whether or not play is a unitary category, (3) the
ambiguous relationship between play and aggression, and (4) the question of whether
play is competitive. The author then suggests an alternative interpretation of
play, that play is a mechanism by which a developing individual can assess its
capabilities.

Abstract: Discusses why the getting-into-shape hypothesis of animal locomotor
play is unlikely, for three reasons. First, all getting-into-shape physiological
responses are very transitory, and disappear shortly after exercise stops. Second,
the kind and amount of exercise performed in play in most species is probably
insufficient to prompt physiological training responses. Third, exercise responses
are not age-limited; animals can exercise and obtain a training response at any
age. Finally, the author suggests a method by which one can evaluate any other
functional hypothesis (e.g., play provides motor learning) about play.

Abstract: Examines the role of the brain and its systems in play behavior in animals.
The author suggests that in addition to lending insight into the evolutionary
origins of play, studies that focus on the neural basis of play behavior can also
be useful in generating testable hypotheses about possible functions of play.
The chapter covers methodological considerations, a lengthy discussion of the
neurochemistry of play, and tentative hypotheses regarding the function of play.